The demands on modern drive systems are increasing more and more. In pick-and-place machines, e.g., smaller and smaller components must be placed more and more precisely on a printed circuit board. In this context, the number of components per unit area of a printed circuit board is increased more and more by miniaturization, so that the speed of the component positioning must constantly increase, as well, in order to maintain as high a throughput as possible at such a machine. In actuality, higher positioning accuracy and simultaneously shorter positioning times are contrary objectives, which may only be achieved by optimally parameterized loops in conjunction with high-quality motors and position-measuring systems.
However, in order to be able to set the parameters of a control loop in an optimum manner, it is important that the knowledge of the drive system is as accurate as possible. One tool for analyzing a drive system is the determination of the transfer function of the drive system or a target system within the drive system. This transfer function describes the attenuation and the phase shift experienced by a signal of a particular frequency applied to the input of the target system, up to the output. The determination of the transfer function (also known as identification) of the drive system or of the target system should be accomplished wherever applicable for the open control loop, since knowledge of the transfer function of the target system in the case of an open control loop allows one to make an assertion regarding the stability of the drive system. However, it is often not possible to open the control loop. Then, an identification must be carried out with a closed control loop. This means that, not the signal applied for test purposes, but rather the difference of the applied signal and the measured, actual value of the controlled parameter, is received at the input of the tested target system.
A conventional method for identifying a drive system is based on applying a noise signal, which contains signal portions in at least all of the frequency ranges important for the specific application, to the input of the drive system. U.S. Pat. No. 5,623,402 describes an example of such an identification. A single excitation signal is generated, which contains portions in different frequency ranges important for the application. In a complex procedure, it may be assured that the excitation signal does not contain any portions, which may lead to the destruction of the drive system, for, when a drive system is excited with noise signals, it must be taken into account that, in certain frequency ranges, considerably more intense responses (resonance) are to be expected than in other frequency ranges, which are more likely attenuated.
It is an aspect of the present invention to provide a method and device, by which the identification of a drive system may be possible in a simple manner.
The above and other beneficial aspect of the present invention may be achieved by providing a method and device as described herein.